Preheat oven to 350 degrees. Line a 9X13-inch pan with aluminum foil and spray with nonstick baking spray with flour.
In a large bowl, stir together 1 cup brown sugar, cornstarch, cinnamon, nutmeg, and ginger. Stir in peaches and lemon juice until combined.
In another large bowl, stir together remaining 1 cup brown sugar, flour, oats, baking powder, and salt. Using a pastry blender cut in butter until crumbly.
In a small bowl, whisk together egg, sour cream, vanilla, and almond extract.
Add egg mixture to flour mixture, stirring until combined.
Press 3/4 cup of flour mixture into bottom of prepared pan. Spread peach mixture evenly on top.
Sprinkle remaining flour mixture on top of peaches.
Bake for 40 to 45 minutes.
Stir together powdered sugar and milk and drizzle over cooled bars.